Self-propelled, electric powered vehicles are typically used in public transportation in light rail and municipal bus use. Electric power is desirable in these vehicles since they are easier to maintain and produce less environmental pollution than vehicles powered by fossil fuels. Improved motor and battery technology has made possible the development of light personal vehicles of limited usefulness, such as short range commuter automobiles. Electric powered vehicles have also found use in amusement rides. Some amusement rides feature self-propelled, electric, track mounted ride vehicles, such as those found in the "Journey into the Imagination" attraction in Epcot Center, Orlando, Fla.
However, conventional self-propelled electric powered vehicles, including amusement rides, suffer from defects which limit their usefulness. A major defect of many, if not all, conventional electric powered vehicles is low conversion efficiency. For example, light rail and municipal electric buses, utilizing overhead catenary wires, consume a large amount of electric power in their operation, but provide acceptable performance over normal terrain because they are not required to carry their power supply. Rather, such vehicles draw electricity from a convenient source disposed along the route typically using conventional bus bar technology.
The inefficient power and motor technology developed for light rail and municipal electric bus type vehicles, is generally not useful for smaller vehicles, especially those which have to carry their own power supply. Portable power supplies, such as batteries, are hampered by technology-inherent inefficiencies which produce a classic "catch-22": to obtain sufficient power to drive the vehicle, the battery must be large; when the battery is large, the weight added by the battery substantially degrades performance. Thus, small, individual electric vehicles which carry their own power supply are hampered by poorer performance, limited range, and the need for time to recharge their batteries.
Conventional electric vehicle amusement rides also suffer similar inefficiencies which limit the level of "thrill" the vehicles are capable of generating. Consumers and amusement ride enthusiasts typically compare electric powered ride vehicles to traditional roller coasters. In general, a more thrilling ride tends to be a more popular ride. Traditional coasters, which are not powered vehicles, achieve thrill by using low speed lift hills, steep drops, and high-speed turns. Tall lift hills and the length of the track required for high speed runout disrupt the esthetics of a themed environment and consume valuable real estate. A self-propelled ride vehicle is desirable because lift hills are not required. Therefore, the amount of track can be reduced, producing a smaller track footprint at a lower cost.
Conventional self-propelled ride vehicles typically use a platen drive. The total tractive effort from such a device is significantly limited by the weight of the vehicle and its payload (e.g., passengers) since that will be the maximum weight applied to the drive wheels to gain traction. This is undesirable because the component of the weight on the drive wheels which contributes to traction on the platen drive (that portion normal to the tractive surface) decreases when the vehicle is on an incline, a time when traction is most needed. Further, when the vehicle moves at speed over hill crests the reduced "G" forces reduce the load weight on the platen drive, thereby reducing the maximum tractive forces which can be applied. If a captive load-track or rail system is used and additional/higher force is applied to the platen drive surface, increased forces result between the vehicle wheels and the load rails which reduce vehicle performance.
Conventional self-propelled ride vehicles cannot provide a thrill equivalent to that experienced in a traditional roller coaster. More specifically, they cannot accelerate above about 0.3 G and travel at nominal driven speeds greater than about 30 mph. Further, their speed is typically achieved only after multiple passes around a relatively short track. Moreover, conventional vehicles cannot accelerate up a hill steeper than about 17 degrees (the arcsin of the ratio of a forward component of the gravitational force acting on the vehicle's mass), nor control acceleration to reverse or stop at any point on the track.
Accordingly, the need exists for a high performance, electric-powered, self-propelled amusement ride which can accelerate up hills steeper than about 17 degrees, and which is capable of providing a thrill which is equal to or greater than that experienced on a conventional roller coaster type amusement ride.